Pump plungers and methods

ABSTRACT

Various embodiments of the invention provide pumps, plungers and plunger assemblies, as well as methods of using them. In accordance with some embodiments, a plunger may comprise a ceramic material and/or may have a facial profile that may allow for more efficient pumping operations. In particular embodiments, for example, a plunger may have a facial profile that allows for deformation of at least a portion of the plunger when the face of the plunger is in contact with a pressurized fluid. Other embodiments provide plunger assemblies, which may comprise a flexible coupling attachment. Yet other embodiments provide pumps comprising such plungers and/or plunger assemblies.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of U.S. patent application Ser. No. 10/422,059 filed Apr. 22, 2003 by J. Mark Chenoweth and entitled “Pump with Ceramic Seal and Methods for Producing” (the “'059 application”), the entire disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to pumps and specifically to components for pumps.

Those skilled in the art will ascertain that pumps generally, and plunger pumps in particular, depend on effective sealing to prevent excessive leakage through the gap between a plunger and any sealing member around the plunger. Without proper sealing, the material being pumped can tend to evacuate the pump chamber along the length of the plunger, instead of through the designed exit port. This leakage not only can reduce the efficiency of the pump, it can create maintenance issues and waste a fairly significant amount of the material being pumped. In fact, significant leakage can sometimes even prevent the operation of the pump itself. Hence, in the past, and in particular with plunger pumps, a variety of packing and/or sealing materials, including Polytetrafluoroethylene (“PTFE”), perfluoroelastomers (including, for example those commercially available from DuPont Dow Elastomers L.L.C.™ under the trade name KALREZ™), and various other polymers, plastics and the like have been used as sealing members to surround the plunger and prevent leakage of the fluid along the plunger.

Unfortunately, however, in order to adequately seal the plunger from leakage, such packing materials usually must maintain contact with the plunger as it moves reciprocally. The packing materials, therefore, tend to degrade relatively quickly (due at least in part to friction between the plunger, the packing material and/or the fluids being pumped, as well as the expendable nature of the packing materials themselves), allowing progressively more leakage over time. Moreover, as the packing materials degrade, there is a tendency by users to tighten the fitting on such pumps periodically, compressing the packing materials to prevent this progressive leakage, which can significantly impact the efficiency of the pump and require more power for operation. Furthermore, over time, the packing materials can, in fact, score the plunger itself, requiring replacement of the plunger, which can be costly and time consuming. This problem, which can be mitigated, but generally not eliminated, by the use of lubricants to reduce friction, is exacerbated by the fact that such pumps often are used in relatively remote locations because of their desirability as being self-powered, such that they can run unattended for relatively long periods of time. Moreover, the use of lubricants imposes additional maintenance overhead and expense, and it presents the danger that the lubricant might contaminate the material being pumped.

As disclosed in the '059 application, many of these issues can be addressed by using a ceramic or similar material for the pump plunger and/or the sealing member surrounding the plunger. Moreover, the applicant has discovered that, by varying various properties of the plunger, additional benefits may be obtained.

Those skilled in the art will also appreciate that there must be some way to communicate the reciprocal driving force of a driving mechanism, such as a motor, etc., to a plunger, in order to reciprocally drive the plunger and thereby effect a pumping operation. In the past, a thrust rod or other device was driven by the driving mechanism, and the thrust rod included some sort of hardware designed to connect with a plunger. Examples of such hardware include threaded attachments, collars, cotter pins, bolts and the like. Often, such hardware requires relatively precise axial alignment between the thrust rod and the plunger, however, to prevent excessive wear of either component. Moreover, such hardware can tend to impose excessive wear on the components, even despite proper alignment, through the repetitive motion inherent to pumping operations. Finally, non-metallic (e.g., ceramic) components sometimes do not tolerate such hard connections as well. Hence, there is a need for another means of translating the motion of a thrust rod (or, for that matter, any driving element) to a plunger.

BRIEF SUMMARY OF THE INVENTION

Various embodiments of the invention provide pumps, plungers and plunger assemblies, as well as methods of using them. In accordance with some embodiments, a plunger may comprise a ceramic material and/or may have a facial profile that may allow for more efficient pumping operations. In particular embodiments, for example, a plunger may have a facial profile that allows for deformation of at least a portion of the plunger when the face of the plunger is in contact with a pressurized fluid. Other embodiments provide plunger assemblies, which may comprise a flexible coupling attachment. Yet other embodiments provide pumps comprising such plungers and/or plunger assemblies.

Merely by way of example, one set of embodiments provides plungers, which may comprise a metal, a ceramic material, etc. and which may be for use in pumps. In some embodiments, a plunger may be generally cylindrical in shape. In other embodiments, the plunger may have other cross-sectional shapes. In particular embodiments, the plunger may have a cross-sectional diameter of between about one-quarter inch and about three inches.

One plunger in accordance with various of these embodiments may comprise a first portion which may be configured to be slidably disposed at least partially within a plunger housing, as well as a second portion. The second portion might have a facial profile defining an opening. In some embodiments, the second portion might be configured to be exposed to a pump chamber and/or in contact with a fluid, such that a reciprocal motion of the plunger with respect to the pump chamber can exert pressure on the fluid, allowing the fluid to be pumped. In particular cases, when the plunger is in contact with the fluid, the fluid may exert sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger.

In accordance with certain embodiments, the plunger has an exterior diameter configured to fit an interior diameter of the plunger housing to within a certain tolerance when no pressure is applied to the facial profile. When the fluid exerts sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger, the deformation may reduces the certain tolerance. In some cases, the sufficient pressure exerted on the facial profile to cause a deformation of the second portion of the plunger may be between about 500 pounds per square inch and about 6000 pounds per square inch. In some embodiments, operation of the plunger may result in a certain amount of leakage of the fluid along the length of the plunger, and/or the deformation of the second portion of the plunger may function to reduce the certain amount of leakage.

In some embodiments, a ratio of a cross-sectional diameter of the opening defined by the facial profile to a cross-sectional diameter of the plunger may be between about 0.3 and about 1.0. In other embodiments, the facial profile may define an opening with a cross-section that is between about one-eighth inch and about three inches in diameter, and/or with a length between about three-eighths inch and about one-and-one-quarter inch. In some cases, the facial profile defines an opening that is roughly hemispherical in shape, and/or the opening can have a diameter that is approximately equal to a cross-sectional diameter of the plunger. In other cases, the facial profile might define an opening with a keyhole shape and/or a channel in a face of the plunger. The length of the channel might span a cross-sectional diameter of the plunger, and/or the width of the channel might be about one-quarter to about three-quarters of a cross-sectional diameter of the plunger. In some cases, the plunger may be configured to be coupled with a flexible coupling assembly.

Another set of embodiments provides plunger assemblies, which can be configured to be used in pumps and/or which can comprise a plunger, including without limitation the plungers described above. In accordance with some embodiments, a plunger assembly may comprise a plunger having an axis, a first end portion and/or a second end portion. The first end portion may be configured to be coupled with a flexible coupling assembly, and/or the second end portion may be configured to be exposed to a pump chamber. Hence, in some cases, a reciprocal motion of the plunger along the axis of the plunger can result in the pumping of a fluid through the pump chamber.

The plunger assembly might further comprise a drive element having an axis and/or a flexible coupling assembly coupled with the first end portion of the plunger and further coupled with the drive element. The drive element may be configured for reciprocal motion along the axis of the drive element, and/or the flexible coupling assembly may be configured to translate the reciprocal motion of the drive element to the plunger, causing a reciprocal motion of the plunger along the axis of the plunger. In particular embodiments, the flexible coupling assembly might comprise a length of flexible tubing. In other embodiments, the drive element might be configured to be coupled with a drive mechanism, which may be capable of providing the reciprocal motion of the drive element.

In some embodiments, the axis of the plunger and the axis of the drive element may be generally axially aligned, and/or the flexible coupling assembly may be configured to allow the axis of the plunger and the axis of the drive element to be aligned relatively imprecisely. In other embodiments, axis of the plunger and the axis of the drive element might not be axially aligned, and/or the flexible coupling assembly may configured to translate the reciprocal motion of the drive element to the plunger, causing a reciprocal motion of the plunger along the axis of the plunger, even though the respective axes of the drive element and the plunger are not axially aligned.

Another set of embodiments provides plunger pump assemblies. In accordance with some embodiments, a pump assembly might comprise a pump body, which might define a pump chamber, perhaps with an inlet port and/or an outlet port. The pump body may further define a plunger port disposed between the inlet port and the outlet port. The assembly can include a first check valve in fluid communication with the inlet port of the pump chamber and/or a second check valve in fluid communication with the outlet port of the pump chamber. The first check valve might be configured to allow a fluid to flow only into the pump chamber and/or the second check valve might be configured to allow the fluid to flow only out of the pump chamber.

In particular embodiments, the pump assembly can further include a plunger housing, which may define a cylindrical bore having an interior diameter. The plunger housing can be disposed within the plunger port. In accordance with certain embodiments, the pump assembly can also include a plunger. In some cases, the plunger can be cylindrical and thus can have an exterior diameter. In particular embodiments, the ceramic plunger is slidably disposed within the cylindrical bore, such that the plunger can be reciprocated back and forth within the bore. Thus, the fluid can be moved from the inlet port of the pump chamber to the outlet port of the pump chamber through the reciprocal action of the plunger. The plunger may be similar to those described above and/or may comprise an end portion with a facial profile defining an opening. In particular embodiments, the plunger and/or the housing may comprise a ceramic material. In some cases, when the end portion of the plunger is in contact with the fluid, the fluid may exert sufficient pressure on the facial profile to cause a deformation of the end portion of the plunger. In other cases, the plunger may be coupled with a flexible coupling assembly, which may be further coupled with a drive system. Hence, the drive system may impart, via the flexible coupling assembly, a reciprocating force on the plunger sufficient to reciprocate the plunger back and forth within the bore.

In a certain aspect, the exterior diameter of the ceramic plunger can fit the interior diameter of the bore to within a certain tolerance (perhaps in the range from about 1.0 microns to about 6.0 microns), and/or the deformation of the end portion of the plunger may sufficient to reduce the certain tolerance. In another aspect, a surface of the plunger may define at least one discontinuity, and/or the discontinuity may be configured to reduce the escape of the fluid through the bore.

In accordance with various embodiments of the invention, a plunger and/or plunger housing can comprise an aluminum oxide. In other embodiments, the plunger and/or housing can comprise transformation-toughened zirconia. Those skilled in the art will recognize that other materials (including without limitation other types of ceramics) can be employed as well, however, without varying from the scope of the invention. Merely by way of example, the plunger and/or the plunger housing can comprise an alumina, comprising 99.5 percent Al₂O₃ a metal, etc.

Another set of embodiments provides fluid injection systems. One exemplary fluid injection system can comprise a plunger pump assembly, perhaps as discussed above, and can further comprise a drive system configured to impart a generally reciprocal force on a plunger. Various embodiments can utilize any of a variety of drive mechanisms. Merely by way of example, in some embodiments, the drive system can comprise a diaphragm motor. The diaphragm motor can be dynamically coupled with the plunger of the pump assembly and can be configured to reciprocally slide the plunger back and forth in the bore of the plunger housing. In this way, the diaphragm motor can operate to move a fluid from the inlet port of the pump chamber to the outlet port of the pump chamber. Some exemplary fluid injection systems can further include one or more fluid sources, some of which can be in fluid communication with the first check valve of the pump assembly and/or with the diaphragm motor. In some cases, some of the fluids can be pressurized.

In one aspect, the diaphragm motor can include a diaphragm and a linkage coupled with the diaphragm. The linkage can also be coupled with the plunger. In such embodiments, a fluid source can be in fluid communication with the diaphragm. Those skilled in the art will appreciate, therefore, that the diaphragm motor can be configured to reciprocally slide the plunger back and forth in the bore in response to a fluid pressure imposed on the diaphragm by the fluid source.

Another set of embodiments provides methods of using a plunger to pump fluids. In accordance with some embodiments, an exemplary method can comprise providing a plunger and/or moving the plunger in a reciprocal motion along an axis of the plunger. The plunger may be similar to those discussed above and/or may comprise a first portion configured to be slidably disposed at least partially within a plunger housing. The plunger may further comprise a second portion having a facial profile defining an opening. In some cases, the second portion may be configured to be exposed to a pump chamber and/or in contact with a fluid, such that a reciprocal motion of the plunger with respect to the pump chamber can exert pressure on the fluid, allowing the fluid to be pumped. When the plunger is in contact with the fluid, the fluid may exert sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger.

In some cases, moving the plunger may result in a certain amount of leakage of the fluid along the length of the plunger, and/or the deformation of the second portion of the plunger may function to reduce the certain amount of leakage. In other cases, the plunger may have an exterior diameter configured to fit an interior diameter of the plunger housing to within a certain tolerance when no pressure is applied to the facial profile. When the fluid exerts sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger, the deformation might reduces the certain tolerance.

In accordance with other embodiments, a method might comprise providing a plunger, which could have an axis, a first end portion and/or a second end portion. The first end portion might be configured to be coupled with a drive element, and/or the second end portion might be configured to be exposed to a pump chamber. Hence, a reciprocal motion of the plunger along the axis of the plunger may result in the pumping of a fluid through the pump chamber. In some embodiments, the method further comprises providing a drive element having an axis; the drive element may be configured for reciprocal motion along the axis of the drive element. In further embodiments, the drive element might be coupled with the first end portion of the plunger, perhaps using a flexible coupling assembly. The flexible coupling assembly might be configured to translate a reciprocal motion of the drive element to the plunger, causing a reciprocal motion of the plunger along the axis of the plunger, and/or the method might include imparting a reciprocal motion to the axis of the drive element, thereby causing the plunger to move in a reciprocal motion along the axis of the plunger.

In particular embodiments, the plunger can be configured to be slidably disposed at least partially within a plunger housing, and/or the second end portion might have a facial profile defining an opening and/or might be configured to be exposed to a pump chamber and in contact with a fluid. In such embodiments, the method can further comprise exerting sufficient pressure on the second end portion of the plunger to cause a deformation of at least part of the plunger. The plunger might have an exterior diameter configured to fit an interior diameter of the plunger housing to within a certain tolerance when no pressure is applied to the facial profile, and/or when sufficient pressure is exerted on the facial profile to cause a deformation of the at least part of the plunger, the deformation might reduce the certain tolerance. Further, operation of the plunger might result in a certain amount of leakage of the fluid along the length of the plunger, and/or the deformation of the second portion of the plunger might functions to reduce the certain amount of leakage.

The invention has been briefly summarized above. A further understanding of specific details and features of the invention may be realized by reference to the remaining portions of the specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating a fluid injection system in accordance with various embodiments of the invention.

FIG. 2 is a sectional drawing of an injector head, including a pump assembly in accordance with various embodiments of the invention.

FIG. 3A is a perspective drawing of a plunger housing and plunger that can be used in accordance with various embodiments of the invention.

FIG. 3B is a perspective drawing of the plunger of FIG. 3A slidably disposed within the plunger housing.

FIGS. 4A and 4B are graphs illustrating, for a variety of fluids, the sealing performance of pump assemblies in accordance with various embodiments of the invention.

FIG. 5 is a schematic drawing illustrating a fluid injection and pump assembly in accordance with various embodiments of the invention.

FIG. 6 is a process flow diagram illustrating a method that can be used to produce a pump assembly in accordance with various embodiments of the invention.

FIGS. 7A-7D illustrate plungers with surface discontinuities along their lengths, in accordance with various embodiments of the invention.

FIGS. 8A-8J illustrate plungers having a variety of facial profiles, in accordance with various embodiments of the invention.

FIG. 9 is a graph illustrating the relative sealing performances of pumps having plungers with a variety of facial profiles, in accordance with various embodiments of the invention.

FIG. 10A is an illustration of a plunger and a thrust rod adapter in accordance with various embodiments of the invention.

FIG. 10B is an illustration of a plunger assembly in accordance with various embodiments of the invention.

FIG. 10C is another illustration of a plunger assembly in accordance with various embodiments of the invention.

FIG. 11 is a process diagram illustrating a method of producing and/or implementing plungers and/or pumps in accordance with various embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Among other things, embodiments of the invention provide plunger pumps, as well as methods for their production. In accordance with certain embodiments, a plunger pump can comprise a pump chamber and a ceramic plunger housing, as well as a ceramic plunger slidably disposed within a bore defined by the plunger housing. In a certain aspect, the outside diameter of the plunger can fit the inside diameter of the housing to within a certain tolerance, and the tolerance can operate to prevent and/or minimize the material being pumped from escaping from the pump chamber through the bore. In another aspect, for a plunger and housing exhibiting a certain tolerance, the length of the housing can be designed to control the rate of any leakage.

According to various embodiments of the invention, a ceramic plunger and housing can operate to allow an essentially leak-proof pumping mechanism without the need for any packing materials, which, those skilled in the art will recognize, can tend to degrade over time, requiring periodic maintenance and/or replacement. Thus, the ceramic housing and/or plunger can provide improved pumping performance over a longer period of time and with less maintenance than traditional plunger/packing arrangements. For instance, pumps according to certain embodiments often consume fewer expendable parts (e.g., packing, packing nuts, etc.) and require less adjustment and/or maintenance (and therefore less travel time for personnel).

In some cases, the plunger and/or housing can be lubricated periodically, and in other cases, the components can be “pre-lubricated,” such that periodic addition of lubricants to the components in unnecessary. In still other cases, the material being pumped can itself act as a lubricant. In further cases, the ceramic plunger and/or housing can be operated without any lubricant at all, since the ceramic materials of which the housing and/or plunger are comprised can be relatively impervious to frictional degradation, and since the tolerance between the plunger and housing reduces the continual frictional contact between the two components. Thus, by reducing frictional contact, both power requirements and component wear can be reduced. Further, ceramic components in accordance with embodiments of the invention can be relatively impervious to temperature, wear, corrosion and reactive chemicals when compared to more traditional materials, such as steel and the like. Hence, pumps in accordance with embodiments of the invention can pump a variety of materials at various pressures and temperatures while exhibiting relatively low power requirements, wear and/or leakage.

Turning now to FIG. 1, an injection system 100 is illustrated in accordance with certain embodiments of the invention. Injection system 100 generally includes an injection head 104 and a drive system 108. The drive system 108 can be any of several drive systems known in the art, including electric motors, lever-operated drives, and the like. In the illustrated embodiment, the drive system 108 comprises a diaphragm motor, which can be used to provide reciprocating action for a plunger in accordance with certain embodiments of the invention, an external housing 112 and a diaphragm cover 116, which can be fixedly attached to housing 112 (e.g., via hex bolts 120 a, 120 b). Although illustrated in FIG. 1 as a cutaway drawing, those skilled in the art will recognize that diaphragm cover 116 and the portion of housing 112 to which it is coupled can form two generally circular, opposing faces.

The diaphragm motor can comprise a molded diaphragm 124 adjacent to a rigid diaphragm plate 128. The diaphragm plate 128 can be fastened to the diaphragm 124, as well as to a linkage 132, perhaps using a hex bolt, to allow movement of the diaphragm 124 (and, therefore, the diaphragm plate 128 as well) to impose generally oscillating lateral forces on the linkage 132, causing it to move reciprocally. The linkage 132 can be fastened to a thrusting rod 136 via a rod adapter 140, and the thrusting rod can include a coupling mechanism 144, that can be coupled with a plunger 148. The plunger 148 can be disposed generally in a pump assembly (e.g., injection head 104), in a manner described in more detail below. The coupling mechanism 144 can, in certain embodiments, comprise a pin. In certain embodiments, as described in more detail below, the coupling mechanism 144 can comprise a coupling assembly, which may be flexible. Also fixedly coupled with the diaphragm plate 128 can be a return spring 152, the function of which is described in detail below.

In some embodiments, the circumference of diaphragm 124 can be sandwiched between diaphragm cover 116 and housing 112 (and, optionally, secured by hex bolts 120 a, 120 b), forming two chambers 156, 160, with a generally airtight seal therebetween. Those skilled in the art will appreciate, therefore, that the diaphragm 124 can be made of any flexible, moldable material that can be used to form an airtight seal, including, for example, silicone, rubber, nylon or the like, using any of a variety of well-known fabrication methods. The diaphragm plate 128 can comprise any rigid material capable of withstanding the sometimes opposing forces imparted by the diaphragm 124 and the return spring 152. For instance, in certain embodiments, the diaphragm plate 128 can be made of steel, aluminum or the like. Those skilled in the art will appreciate that the return spring 152 can comprise any material of sufficient strength that is capable of remaining elastic under repetitive compressive loads, such as, merely by way of example, a cadmium-plated carbon steel.

The linkage 132 can be coupled with a reciprocating mechanism 164 by a stirrup assembly 168, which can be attached to the reciprocating mechanism 164 with a pin and can define a collar around the linkage 132, secured, for example, by a set screw. The use of such a stirrup assembly is known to those skilled in the art and therefore will not be described in further detail. In this way, any lateral movement of the linkage 132 can be translated to a toggling force on the reciprocating mechanism 164.

In general, reciprocating mechanism 164 can be any mechanism and/or device that operates to translate a constant fluid pressure into a generally oscillating force, and, in some embodiments, can operate by a toggling mechanism. Merely by way of example, reciprocating mechanism 164 can comprise a “flipper” spring valve known to those skilled in the art. Reciprocating mechanism 164 can be coupled with a fluid source via an adapter (not shown on FIG. 1), such as a ¼″ threaded female receptacle known to those skilled in the art. In this way, the reciprocating mechanism 164 can receive a pressurized fluid. The reciprocating mechanism also can be coupled with both an exhaust vent 170, as well as to a pilot line 172, which can provide fluid communication from reciprocating mechanism 164 to the chamber 156. In this way, reciprocating mechanism 164 can provide switchable fluid communication between the pressurized fluid source, the chamber 156 and the exhaust vent 170.

Embodiments of the invention can be configured to operate with a variety of pressurized fluids. (It should be noted as well that other means can be used, including lever action, electrical and/or gas motors, etc.) Often such fluids can be gases, such as pressurized air, natural gas, wellhead gases, and the like, but they can, in accordance with some embodiments, be liquids as well. In some embodiments, the fluid can be pressurized to any suitable pressure, which, in some embodiments can be about 15-150 psi, and/or a regulator can be used to reduce the operating pressure of the gas. Merely by way of example, fluid injection systems in accordance with various embodiments can be used to inject an additive into a pressurized fluid stream, such as a gas line or the like. In such embodiments, a pilot line branching off of the main gas line can be the source of pressurized fluid to drive the diaphragm motor.

In a default state, return spring 152 is under no compression, diaphragm plate 128 is disposed proximate to diaphragm cover 116, and the reciprocating mechanism 164 is configured (as a result of the position of the linkage 132) to route the pressurized fluid toward the chamber 156. In operation, when a pressurized fluid source is attached to the reciprocating mechanism 164, the fluid flows from the reciprocating mechanism 164, through the pilot tube 172 and the adapter 176, into the chamber 156. The fluid can create sufficient pressure in the chamber 156 to displace the diaphragm 124 away from the diaphragm cover 116, thereby placing the return spring 140 under compression. This displacement will also cause the linkage 132 to move generally away from the direction of the diaphragm cover 116 and toward the injection head 104.

At a certain point, (i.e., when the diaphragm 124 has moved sufficiently far away from to the diaphragm cover 116), the linkage 132 will have completed a full forward stroke, displacing trip stirrup 168, thrusting rod 136, and, by extension, plunger 148. At this point, the displacement of trip stirrup 168 will toggle the reciprocating mechanism 164. When toggled, the three-way valve of the reciprocating mechanism 164 will operate to close the connection between the pressurized fluid source and the chamber 156 and will instead allow the pressurized fluid already in chamber 156 to vent to the environment (and/or a suitable collection device) through exhaust vent 170, thereby acting to reduce the pressure in the chamber 156. The other chamber 160 can be vented to the atmosphere, for instance, through vent 180, to maintain roughly atmospheric pressure in that chamber 160, preventing any positive or negative pressure therein from affecting the movement of the diaphragm 124.

When the pressure in the chamber 156 has decreased sufficiently, the force imposed on the diaphragm plate 128 by that pressure will be overcome by the force of the loaded return spring 152, causing the plate 128 (and, in connection, the diaphragm 124) to return to the default position, forcing the linkage 132 to reciprocate toward the diaphragm cover 116 and away from the injection head 104, thereby displacing trip stirrup 168 toward its default position and moving the thrusting rod 136 and plunger 148 in the direction of the injection head 104. (Alternatively, instead of using a return spring 152, the diaphragm motor can be configured so that pressurized fluid can be routed alternately to chambers 156 and 160, thereby producing a similar reciprocal effect on the diaphragm 124.) When the linkage 132 has reciprocated to the extent of its back stroke, the displacement of the trip stirrup 168 will again toggle the reciprocating mechanism 164, causing the process to repeat. In this way, the diaphragm motor, as described generally above, can produce a reciprocating action of the linkage 132 when exposed to a constant pressure fluid source. Via the thrust rod 136, the reciprocating action of the linkage 132 can cause the plunger 148 to move reciprocally within the injector head 104.

As discussed in detail below, the plunger 148 contacts the fluid to be injected, which can be a different fluid than the pressurized fluid used to drive the diaphragm motor, discussed above. Merely by way of example, materials that can be injected using embodiments of the invention include surfactants, defoamers, biocides (including bleach), corrosion inhibitors (including toluene, xylene, etc.), demulcifiers, solvents, paraffin inhibitors, scale inhibitors, pH buffers, hydrogen sulfide scavengers, water clarifiers, coagulants, methanol, acids (including, in particular, hydrochloric, phosphoric and acetic acids), alcohols (including, in particular, methanol), and the like. Hence, a wide variety of materials can be pumped/injected by embodiments of the invention, and, in some cases, a small amount of the material to be injected might escape the injector head 104 via transmission along the plunger 148. To accommodate such situations, and/or to allow the monitoring of any leakage (e.g., for maintenance purposes), the housing 112 can define a drain 184 to collect and/or allow the escape of leakage.

Turning now to FIG. 2, an injection head 104 in accordance with various embodiments of the invention is illustrated. The injection head 104 can generally comprise a pump assembly, including a pump body 200. The injection head 104 can be attached to a drive mechanism, such as the drive system 108 of FIG. 1, to form an injection system such as that represented by reference numeral 100.

The pump body 200 can define a pump chamber 204, which can have an inlet port 208 and an outlet port 212. The inlet port 208 can be in fluid communication with a check valve 216, known to those skilled in the art, and pump body 200 can include an attachment mechanism 200, which may be a threaded bushing, etc., for attaching a supply line to be in fluid communication with the inlet port 208 through the check valve 216. Thus, when in operation, as discussed below, the injection head 104 can draw fluid from the supply line, and the check valve 216 can prevent the backflow of any fluid from the pump chamber 204 into the supply line. Likewise, the outlet port 212 can be in fluid communication with a check valve 224, and further in fluid communication with a discharge line, through attachment means 228. Either check valve 216, 224 can be a suction ball assembly, which, as those skilled in the art will recognize, will effectively allow for one-way transmission of fluid. If necessary, check valve 224 can include a spring to provide increased resistance and further ensure against backflow into the pump chamber 204. Optionally, injection head 104 can include a threaded priming key 236, which, when backed out of the priming port 240, will create a small vacuum in the pump chamber 204, drawing fluid through the inlet port 208 and thereby priming the injection head 104 for pumping.

The pump body 200 can further define a plunger port 244, which, in certain embodiments, extends from the exterior of the pump body 200 to the pump chamber 204. As illustrated in FIG. 2, the plunger port 244 can define a relatively narrow void extending away from the pump chamber 204 and can define a wider void near the exterior of the pump body 200. The plunger port 244 can be adapted to hold a plunger housing 248 within the wider void. Generally, the plunger housing 248 can fit relatively tightly within the plunger port 244 in order to prevent excess leakage of fluid from the pump chamber 204. As discussed in greater detail below, the relative sizing of the plunger housing 248 and the interior of the plunger port 244 can, in some cases, be designed to place the plunger housing under compression. In certain embodiments, a cap 252 can be used to secure the plunger housing 248 within the plunger port 244. In other embodiments, the cap can serve additional purposes. For instance, the cap 252 could be designed to attach to the pump body 200 with a compression fitting, such that attachment of the cap 252 could be used to place the plunger housing 248 under compression. In still other embodiments, the cap 252 can comprise a fitting for attaching the pump insertion head 104 to a drive mechanism, such as the diaphragm motor of FIG. 1.

A plunger 148 can be slidably disposed within the plunger housing 248, such that, when fully inserted, the plunger 148 extends through the pump chamber 204 (e.g., proximate to the far wall of the pump chamber 204), effectively displacing a substantial proportion of the volume of the pump chamber 204. The plunger 244 can, thereafter, be withdrawn from the pump chamber 204, effectively removing the displacement and thereby creating a state of relative vacuum in the pump chamber 204 and drawing fluid from the inlet port 208. When reinserted in the pump chamber 204, the plunger 148 can again displace a substantial proportion of the volume of the chamber 204, forcing at least a portion of the fluid in the pump chamber 204 through the outlet port 212 (the check valve 216 can prevent discharge through the inlet port 208. In this fashion, if moved in and out of the pump chamber 204 with a reciprocating action, plunger 148 can be used to pump fluid from the inlet port 208 through the pump chamber 204, to the outlet port 212. Thus, when coupled with a drive system motor, such as that illustrated in FIG. 1, the injector head 104, through the action of the plunger 148, can be used to pump a fluid from a supply line to a discharge line, and can further be used to inject a first fluid into a second fluid. In some cases, the second fluid can be the pressurized fluid that powers the diaphragm motor, allowing for an essentially self-powered injection system.

In accordance with certain embodiments, the plunger 148 and/or plunger housing 248 can comprise a ceramic material. In many cases, the plunger 148 and housing 248 will comprise like materials, although in other cases, the plunger 148 and the housing may comprise different materials. Merely by way of example, in a particular embodiment, plunger 148 and/or plunger housing 248 can comprise an alumina ceramic. There are a variety of such compounds commercially available, including, for instance, a ceramic blend commonly known in the art as AD-995, which, those skilled in the art will appreciate, generally comprises about 99.5 percent Al₂O₃. AD-995 is commercially available from Coorstek, Inc., of Golden, Colo. Those skilled in the art will further recognize that other alumina compounds can be used as well. For example, certain embodiments of the invention employ a plunger 148 and/or housing 248 made of a ceramic comprising approximately 99.8 percent Al₂O₃, known in the art as AD-998, and/or an alumina comprising approximately 98.5 percent Al₂O₃, known in the art as FG-995, all available from Coorstek.

In still further embodiments, other ceramics can be used as well, including, for example, those comprising aluminum oxide. Some such ceramics further comprise proportions of zirconia, and one exemplary embodiment employs a material known in the art as transformation toughened zirconia (“TTZ”), also commercially available from Coorstek. Those skilled in the art will recognize that TTZ can, in some cases, be partially stabilized, for instance, by the introduction of certain proportions of MgO. Various embodiments can comprise other types of zirconia and/or alumina compounds, such as those known in the art as tetragonal zirconia polycrystals (“TZP”), yttria stabilized zirconia polycrystals (“YTZP”), ceria stabilized tetragonal zirconia polycrystals (“CeTZP”), other ceria compounds, and/or zirconia toughened aluminas (“ZTA”). Those skilled in the art will recognize, based on the disclosure herein, that other ceramic materials may be used as well, including for instance, silicon carbides and tungsten carbides. In certain aspects, such materials often will have a relatively low co-efficient of thermal expansion and/or a relatively high degree of abrasion resistance. In some cases, the plunger and/or the plunger housing can be coated in order to improve performance parameters such as wear resistance, coefficient of friction, etc. Virtually any desired material can be used as a coating, although monolithic materials are used most often. In particular cases, any of the materials discussed above can be used as a coating material, depending on the requirements of specific implementation. In yet other embodiments, the plunger and/or plunger housing may comprise a metal, such as aluminum, steel, and/or any of several alloys.

Turning briefly now to FIG. 3A, a perspective drawing of the plunger 148 and the plunger housing 248 is illustrated. As illustrated, the plunger housing 248 can describe a bore, which, in some embodiments, can be generally circular, having an interior diameter D₁. The plunger 148, on the other hand, can have an exterior diameter D₂. In accordance with some embodiments the diameter D₂ of a plunger may be between about one-quarter inch and about three inches. In other embodiments, the diameter D₂ may be between about three-eighths inch and two inches, and in still other embodiments, the diameter D₂ may be between about one-half inch and one and one-half inches. Of course, embodiments of the invention are not limited to any particular sized plungers.

Generally, the exterior diameter D₂ of the plunger 148 will be smaller than the interior diameter D₁ of the bore, such that the plunger 148 can be slidably disposed within the plunger housing 248, as illustrated, for example, in FIG. 3B. In accordance with some embodiments of the invention, the plunger 148 and/or plunger housing 248 can be manufactured so that the tolerance (i.e., clearance) between D₁ and D₂ is within a few microns. For example, in certain embodiments, the tolerance between D₁ and D₂ can be in the range of about 1.2 microns to about 1.8 microns. In other embodiments, the tolerance between D₁ and D₂ can be in the range of about 1.47 microns and about 2.45 microns. In some embodiments, as discussed above, the plunger 148 and/or housing 248 can be manufactured of ceramic materials, which, those skilled in the art will recognize, can have a relatively low coefficient of thermal expansion, allowing for relatively precise tolerances even in applications where the plunger 148 and/or housing 248 might be subjected to variations in temperature.

In some embodiments, as discussed below, in addition to the tolerance between D₁ and D₂, the length L of the housing 248 can impact the ability of the housing to prevent leakage of the material being pumped. Generally, the longer the plunger housing 248, the lower the rate of leakage that would be expected for a plunger and housing having a given tolerance. Thus, for pumps operating with materials with lower Reynolds numbers and/or pumps operating at higher pressures, either a tighter tolerance between the plunger and the housing and/or a longer housing can be employed to further assure against unacceptable leakage rates. In some exemplary embodiments, the plunger housing can be between 0.5 and 10.0 cm, although longer and/or shorter housings can be used, depending on operating conditions, as discussed herein. Moreover, as discussed in detail below, the characteristics of the facial profile and/or outer surface of the plunger 148, as well as the inner surface of the plunger housing 248, can be modified to effect different leakage rates of different materials.

Returning now to FIG. 2, the tolerance between the exterior diameter of the plunger 148 and the housing 248 can allow the plunger 148 and the plunger housing 248 to be used in the operation of the injection head 104 without the need for any seals, gaskets or lubricants. In effect, the relatively precise tolerance between the two parts can allow the plunger 148 to reciprocate freely within the plunger housing 248, in the manner described above, while preventing any substantial leakage of fluid through the bore of the plunger housing 248. (Of course, any fluid that does leak through the bore can be collected and/or evacuated through drain 180, as described above with regard to FIG. 1). Those skilled in the art will recognize that the amount of leakage through the bore depends on the properties of the fluid in pump chamber 204, including the pressure imposed on the fluid and the Reynolds number of the fluid, as well as the length of the plunger housing 248 and the tolerance between the exterior diameter of the plunger 148 and the interior diameter of the housing 248.

FIGS. 4A and 4B depict charts (400 and 404, respectively) illustrating a set of calculated leakage rates (also known in the art as “blow by” rates) for particular embodiments of the invention, with respect to several exemplary fluids. FIG. 4A illustrates the calculated rates at which four different fluids could be expected to blow through the bore of an exemplary plunger housing during operation of the injector head. The exemplary plunger housing used to calculate the rates is 1.158 inches in length and can accommodate a 0.375 inch plunger with 1.27 microns of clearance on either side (for a total of 2.54 microns tolerance). The calculated values exhibited in FIG. 4A assume that the plunger has a face that is flat and perpendicular to the length of the plunger and that the plunger includes no discontinuities along its length. For relatively low-viscosity fluids, such as Methanol, under relatively high pressure, somewhat greater leakage rates might be expected (slightly more than 0.7 cm³ per minute at a pressure of 6000 psi). On the other hand, with more viscous fluids (for example, with ethylene glycol), even at such high pressures, very little leakage would be expected. Given the disclosure herein, those skilled in the art will recognize that increasing the length of the housing and/or decreasing the tolerance between the plunger and the housing can reduce the expected leakage rates.

For instance, FIG. 4B includes a chart 404 depicting calculated data for an exemplary plunger housing similar to the plunger housing analyzed in FIG. 4A, except that the tolerance between the plunger and the housing is 0.127 microns (total). As illustrated by the chart 404, the leakage rates for this embodiment are almost an order of magnitude lower than those for the exemplary plunger of FIG. 4A. In this way, those skilled in the art will appreciate, reducing the clearance between the plunger housing bore and the plunger can provide significant improvements in leakage performance. Those skilled in the art will recognize, as well, that a longer plunger housing likewise will lead to reduced leakage. In addition, as discussed below, altering the facial profile of the plunger and/or introducing discontinuities in the surface along the length of the plunger can affect expected leakage rates as well.

Turning now to FIG. 5, an alternative embodiment of a pump 500 in accordance with the present invention is illustrated. The pump 500 generally comprises a power head 504 and a pump body 508. The power head can include any drive system (not shown). A piston-plunger assembly 516 is disposed within the power head 504, with the plunger portion 520 of the assembly 516 extending into the pump body 508. The drive system can be any device that is capable moving the piston-plunger 516 vertically in a generally reciprocal fashion (including without limitation the drive systems described elsewhere in this disclosure), and it can be integrated with the power head 504, or alternatively, can be a separate device that can be attached via suitable fastening apparatus. The power head 504 can be securely and/or removably attached to the pump body 508, using fasteners such as bolts, locknuts and the like. In certain embodiments, the power head 504 can be coupled with the pump body via a threaded attachment member 522. Optionally, a stroke-limiter 524 can be implemented in the power head 504, to limit the length of the stroke of the piston-plunger 516 and thereby control the pump rate, pump chamber pressure, etc.

The reciprocating mechanism 512 can be coupled with the piston plunger 516 in any of several different ways. For instance, in certain embodiments, the reciprocating mechanism 512 can be an electric motor with a linkage, and the linkage can be coupled with the piston plunger 516. Methods of coupling an electric motor to a piston to produce a generally reciprocal motion are well known in the art and will not be discussed in detail herein. In other embodiments, the reciprocating mechanism 512 can comprise a device similar to the toggling switch discussed in conjunction with FIG. 1, and can be in fluid communication with a pressurized fluid source. In such embodiments, the reciprocating device 512 can be operable to pressurize/depressurize, in oscillating fashion, a chamber 528 within the power head 504, forcing the piston plunger 516 downward against a return spring 532, which, when the pressure in the chamber 520 is reduced, can force the piston-plunger 516 up to its original position.

Other means of imparting reciprocal motion to the piston-plunger 516 (including manual manipulation of the piston-plunger 516, in which case, the reciprocating mechanism 512 could be a lever coupled with the piston-plunger 516) can be incorporated within the scope of the invention as well. Those skilled in the art will recognize that certain illustrated components, such as, for example, return spring 532, may be considered optional, and other components well known in the art can be included, depending on the nature of the reciprocating mechanism 512, so long as the chosen device operates move piston-plunger 516 in a vertical, generally reciprocal fashion.

The pump body 508 can define a pump chamber 536 having an inlet port 540 and an outlet port 544, as well as an optional bleeder valve 548. The inlet port 540 and the outlet port 544 each can have a check valve (552 and 556, respectively), and the inlet port 540 can be in fluid communication (perhaps through the check valve 552) with an adapter 560 for attachment to a line supplying the material to be pumped. Likewise, outlet port 544 can be in fluid communication (e.g., through the check valve 556) with an adapter 564 for a discharge line. The discharge line optionally can be configured to feed into a pressurized line, so that pump 500 can be used to inject additives, etc. into pressurized fluid streams. As discussed above, in certain embodiments, the pressurized fluid stream can be used to power the reciprocating device 512, such that pump 500 can use the pressure of a fluid stream itself to introduce additives into that stream.

In the illustrated embodiment, the pumping operation is similar to that described above. The plunger portion 520 can be drawn out of the pump chamber 536 by the action of the reciprocating device 512, creating negative pressure in the pump chamber 536. The negative pressure will draw fluid through the inlet adapter 560, check valve 552 and inlet port 540, into the pump chamber 536. When the piston-plunger has reached the end of its upward stroke (e.g., when it strikes stroke limiter 524), it will begin a downward stroke. Prevented by the check valve 552 from escaping the pump chamber 536 through the supply line, the material in the pump chamber will be evacuated through the port 554, check valve 556 and adapter 564, perhaps to an attached discharge line.

To stabilize the plunger 520 and/or prevent migration of pumped material out of the pump chamber 536 and along the axis of the plunger 520, a plunger housing 572 can be employed. The plunger housing 572 can be situated within a plunger port 576 defined by the pump body 508, and the housing 572 can define a bore (which, in some cases, can have a generally circular cross section and therefore can be generally cylindrical in shape), similar in some ways to the housing discussed above with respect to FIGS. 3A and 3B. In accordance with certain embodiments, the plunger portion 520 (and/or the entire piston-plunger 516), as well as the plunger housing 572, can be constructed from a ceramic material, including without limitation the materials discussed in detail above. The plunger 520 can be designed to be slidably disposed within the plunger housing, to within a clearance (i.e., tolerance), perhaps of a few microns. In certain embodiments, the clearance can be within about 0.6 microns per side (1.2 microns total) to about 1.5 microns per side (3.0 microns total). In this way, the plunger housing 572 can provide sealing capabilities to prevent leakage of any significant amount of pumped material without the need for any additional packing material, reducing the cost and complexity of maintenance. Moreover, certain embodiments eliminate the need for any sort of lubricating agents, often used in the past to reduce friction between the plunger and any associated packing materials, although in certain embodiments, lubricating agents (perhaps including the fluid being pumped) still can be used if desired.

In some embodiments, the plunger housing 572 optionally can be placed under compression by the plunger port 580. This compression can be achieved, in some cases, by heating the plunger port 580 prior to inserting the plunger housing 572 into the plunger port 580. Other embodiments secure the plunger housing using other means, for instance through use of an adhesive, press fitting, capping and/or the like. For instance, in an embodiment where the pump body 508 is attached to the power head 504 using a threaded attachment method (e.g., 522), the plunger port 580 can be integrated into the threaded portion of the pump body 508, and attaching the pump body 508 to the threaded attachment 522 can operate to place the plunger port 580, and by extension, the plunger housing 572, under compression. Regardless of the method of compressing the plunger housing 572, however, those skilled in the art will recognize that the compression of housing 572 can, in some cases, operate to reduce the clearance between the housing 572 and the plunger 520. In such cases, the housing 572 and/or plunger 520 can be designed to accommodate changes to the interior diameter of the plunger housing anticipated as a result of the compression of the housing 572.

As discussed above, the length of the plunger housing 572 can affect the sealing performance of the housing, and various embodiments of the invention therefore can employ plunger housings of varying lengths, depending on anticipated pressures within the pump chamber 536. In particular embodiments, the design of the plunger housing 572 (e.g., the housing's length, the clearance between the housing and the plunger, etc.) can take into account the type of material to be pumped.

As alluded to above, in certain cases it can be helpful to have as close a fit as possible between a plunger port and a plunger housing, and ceramic materials can be used to obtain a precise fit. In accordance with certain embodiments of the invention, therefore, a method is provided for producing a ceramic plunger pump assembly. In some embodiments, methods for producing plunger pump assemblies can be used to create new pumps and/or injector heads, and, in particular, can be used to produce injector heads for any of the variety of “Texsteam™”-style pumps known in the art. In other embodiments, similar methods can be used to retrofit existing injector heads, pump bodies, etc. in order to accommodate ceramic plungers and/or plunger housings in accordance with various embodiments. For instance, the FloMore™ Series 5200 injector head, commercially available from Richart Distributors Inc. of Oklahoma City, Okla., could be retrofit in accordance with some embodiments of the invention. Similarly, the Series 5100 air or gas driven injectors from Texsteam Corporation™ of Houston, Tex. can be retrofit in accordance with other embodiments of the invention, and the Model 40/60/80 D-Series of pumps commercially available from Sidewinder Pumps, Inc.™ of Lafayette, La., can be retrofit according to certain embodiments of the invention.

FIG. 6 illustrates an exemplary method 600 for producing a ceramic plunger pump assembly in accordance with embodiments of the invention. According to method 600, a pump body is provided at block 604. The body can be, merely by way of example, the pump body 200 of FIG. 2. At block 608, the pump body optionally can be heated from an ambient temperature to a temperature sufficient to cause expansion of the pump body, and, in particular, expansion of the plunger port. Those skilled in the art will recognize that the temperature to which the pump body ideally should be heated can vary according to the material from which the pump body is constructed. In a particular embodiment, a temperature in the range of about 200° F. to about 700° F., can cause sufficient expansion of the plunger port. In other embodiments a temperature in the range of about 300° F. to about 500° F. might be more suitable. In still other embodiments, a different temperature and/or range of temperatures may produce the best results. Those skilled in the art will recognize that, if desired, only that portion of pump body 200 that defines plunger port 244 need be heated.

Those skilled in the art also will recognize that heating the pump body can be accomplished by a variety of methods. For instance, a portable acetylene torch can be used to heat the portion of the pump body local to the plunger port. In other embodiments, the entire pump body might be heated in an oven. In still other embodiments, an exothermic chemical reaction could be used to apply heat to a specific portion of the pump body, and/or an induction coil might be used to heat a specific portion of the body. Any suitable method of heating the pump body can be employed without varying from the scope of the invention.

At block 612, a plunger housing (e.g., 248) can be inserted into the plunger port of the pump body. In accordance with some embodiments, the insertion procedure can be as simple as sliding the plunger housing into the plunger port. In other embodiments, the plunger housing and/or the plunger port can be threaded and/or otherwise adapted to be mated together, and insertion can comprise threading the housing into the port, etc. In a particular embodiment, the plunger port might employ a ridge or other positive fastening mechanism, and inserting the plunger housing can involve ensuring that the positive fastening mechanism has been engaged (i.e., inserting the plunger housing until it “clicks” into proper position).

Optionally, in accordance with certain embodiments, the pump body can be allowed to cool (block 616). If, for example, the pump body had been heated above the ambient temperature before the plunger housing was inserted, allowing the pump body to cool after insertion can cause the pump body to contract, producing a tighter seal between the plunger port and the plunger housing than might otherwise be obtained. In some cases, depending on the relative sizes of the plunger port and the plunger housing, cooling the pump body can effectively place the plunger housing under compression (block 620). Placing the plunger housing under compression not only can improve the seal between the plunger port and the plunger housing, but it also can greatly improve the burst strength of the of plunger housing, allowing it to withstand, for example, greater fluid pressures in the pump chamber. In effect, the tensile strength of the (often metallic) pump body and the compressive strength of the plunger housing can compliment one another, allowing for improved overall durability of the pump.

As discussed above, in accordance with certain embodiments, compressing the plunger housing can, in fact, reduce the size of the bore defined by the plunger housing, thereby reducing the clearance between the plunger housing and a plunger slidably disposed within the plunger housing. Hence, the manufacturing process of the plunger and/or plunger housing can account for this compression, and/or the design the plunger and/or plunger housing can be altered to incorporate marginally more clearance than otherwise would be desired.

At block 624, a plunger can be slidably disposed within the plunger housing in a fashion such that it can be moved into a pump chamber to perform the functions outlined above. Optionally, a capping device (such as the cap 252, illustrated on FIG. 2) can be attached to the plunger port to secure the plunger housing within the plunger port and/or to provide a means of attachment of the pump assembly to, for instance, a diaphragm motor. At block 632, the injector head can be attached to a powering device, for example, the drive system 108 of FIG. 1, which can be used to reciprocate the plunger and effectuate the pumping action described above.

In accordance with some embodiments of the invention, a plunger can be manufactured to have one or more discontinuities along the outer surface of the length of the plunger. These discontinuities can be filled with a packing material (e.g., a viscous fluid such as oil) before and/or during operation of the pump in order to provide a further seal against leakage of the material being pumped. For instance, in some cases, (e.g., where a relatively viscous material is being pumped), the discontinuities might be left empty prior to operation of the pump, and any pumped material leaking along the length of the plunger can fill the discontinuities, thereby effectively providing a seal again further leakage along the length of the plunger.

In other cases (e.g., where the pumped material has a relatively low viscosity), the discontinuities can be filled with a relatively more viscous packing fluid and/or lubricant prior to operation of the pump. This packing fluid/lubricant effectively can serve as a seal to block leakage of the pumped material along the length of the plunger. In either case, the material filling a discontinuity in the surface of the plunger can occupy the discontinuity as well, perhaps, as the clearance (i.e., the tolerance) between the plunger and the housing. In accordance with some embodiments of the invention, therefore, the discontinuities can be disposed on a portion of the plunger that remains within the housing during the entire stroke of the plunger, such that any material disposed within the discontinuities can maintain contact with the housing, whether the plunger is extended into the pump chamber or withdrawn from the pump chamber. In alternative embodiments, the housing itself might comprises similar discontinuities on the surface of the bore, and the plunger itself might have no discontinuities.

As mentioned above, the discontinuities are optional; in many embodiments, the plunger has no discontinuities. Moreover, the number of and nature of the discontinuities is discretionary and can vary by application. Implementations with a higher tendency for leakage (e.g., those with a relatively short housing and/or a relatively large clearance between the plunger and the housing, as well as those in which a relatively low viscosity fluid is pumped at relatively high pressures, as illustrated by FIGS. 4A and 4B) might have more discontinuities than other implementations. Likewise, the discontinuities can have any of a variety of cross-sectional profiles, some of which may be more appropriate under certain circumstances than others.

For example, FIG. 7A illustrates the side view of a plunger 700, which has been manufactured to incorporate discontinuities 704 a, 704 b, along the length of the plunger. In the embodiment illustrated by FIG. 7A, the discontinuities 704 have a profile that generally can be described as V-shaped, exhibiting a progressive narrowing of the circumference of the plunger from a larger outside diameter D₂ to a smaller diameter D₃ as illustrated on FIG. 7B. Those skilled in the art will recognize, however, that in other circumstances difference cross-sectional profiles may provide a more effective seal against excess leakage. For instance, FIG. 7C illustrates another plunger 708 having a single discontinuity 712 with a square cross-sectional profile, such that, along the length of the plunger 708, the discontinuity 712 represents an abrupt transition from an outside diameter D₂ to a narrower diameter D₃. Those skilled in the art will also recognize that in still other embodiments discontinuities having different cross-sectional profiles may be utilized, which can be, merely by way of example, U-shaped and/or the like. The number of discontinuities is discretionary and can be varied in accordance with needs of particular implementations and/or as the result of empirical testing under various circumstances.

In accordance with further embodiments of the invention, the end of the plunger that is placed into the plump chamber can include a variety of different faces (also described as “facial profiles”), irrespective of the composition of the plunger and/or housing. For example, as in the embodiment illustrated by FIGS. 3A and 3B, a plunger can have a flat face that describes a perpendicular angle with the length of the plunger. In other embodiments, however, the face of the plunger can be convex, conical (i.e., pointed), etc. In still further embodiments, the face of the plunger can be concave, be notched and/or have any of a variety of cut-outs. In such embodiments, depending on the composition of the ceramic comprising the plunger, the variation in the face profile can allow for the deformation of part of the plunger, which, in some cases can serve to reduce the tolerance between the end of the plunger and the housing when substantial fluid pressure is applied to the face of the plunger (as during pumping operations). While in the past, ceramic materials may have been considered too brittle and/or too rigid to permit such deformation on a consistent satisfactory basis, experimental testing has revealed that certain facial profiles, as described herein, may be used with a variety of modern ceramic materials. (It should be noted, however, that embodiments of the invention are not limited to ceramic materials.)

Deformation of the plunger in this way can, therefore, further reduce the amount of leakage of the pumped material along the length of the plunger. It should be noted that, while such plungers may be used in any of the injector heads and/or pumps described above, the applications of such plungers are not limited to such embodiments but may include any pump, especially those in which relatively high fluid pressures may be expected, including without limitation centrifugal pumps, piston pumps, reciprocating plunger pumps, double-acting plunger pumps and/or the like.

FIGS. 8A-8J illustrate several embodiments of plungers having faces of varied plunger face configurations, each of which can, in certain circumstances allow for deformation of the end of the plunger. For example, FIG. 8A illustrates a plunger 800 including a notch 804. A cross-sectional view of the plunger 800 and notch 804 is provided in FIG. 8B. In this exemplary embodiment, a high fluid pressure applied to the face of plunger 800 (and, necessarily, to the surfaces of notch 804 as well) can force either side of the plunger 800 to deform away from the notch 804, effectively increasing the cross-sectional diameter of the plunger 800 and thereby reducing the tolerance between the plunger and the housing.

In still other embodiments, for example, those illustrated in FIGS. 8C and 8D, a plunger 808 can have a generally concave and/or hemispherical face 812 (i.e., the facial profile can describe a generally hemispherical opening). Merely by way of example, in some embodiments, the diameter of the hemispherical face may be approximately equal to the cross-sectional diameter of the plunger itself (such that, at its widest point, at or near the end portion of the plunger, the opening is approximately as wide as the plunger itself. Alternatively, the opening may be some fraction of the face; merely by way of example, the ratio of the opening's diameter to the cross-sectional diameter of the plunger can range from virtually 0 to nearly 1.0, depending on the material used and the amount of deformation desired. FIGS. 8E and 8F show an exemplary plunger 816 having a facial profile 820 defining a hemisphere, such that this ratio is approximately 0.8.

Another facial profile can define an opening that is generally cylindrical in shape. For instance, FIGS. 8G and 8H depict a plunger 808 with such a facial profile. In some embodiments, the plunger can have a diameter of about one-quarter inch to about three inches, and in particular between about three-eighths inch and about five-eighths inch; the cylindrical opening can be between about one-eighth inch and about two inches in diameter. In particular embodiments, the plunger can have a diameter between about one-quarter inch and about one inch, and the cylindrical opening can have a diameter between about one-eighth inch and about three-eights inch. In other embodiments, the cylindrical opening can extend between about one-eighth inch and about two inches into the plunger, and in particular between about three-eighths inch and about one and one-eighth inches.

Other facial profiles may be used as well. Merely by way of example, in particular embodiments, (for example, the embodiment illustrated by FIGS. 8I and 8J) a plunger 832 can have with a “keyhole” cutout, such that the face of the plunger includes a relatively narrow opening 836 that widens as it extends into the plunger 832 to describe a relatively larger void 840 within the plunger. Such embodiments can be used, under some circumstances, to cause deformation along a greater length of the end of plunger 832 and/or can be varied as desired to accomplish the intended deformation profile of the plunger 832.

The dimensions above represent values that have proven to be effective in certain applications. Those skilled in the art should appreciate, however, that these values, which can be appropriate for certain implementations, may be modified as appropriate in other circumstances, depending, for example, on the viscosity of the fluid being pumped, the size of the plunger, the flow rate of the pump, and/or other application-specific factors. Moreover, although the openings above have been described as cylindrical, hemispherical, etc. for ease of description, other embodiments of the invention can feature different variations on these profiles. Merely by way of example, in some embodiments, it may be advantageous for a profile to be more or less concave than a true hemisphere (such that the opening describes half of an ellipsoid). Likewise, a generally cylindrical opening may have a roughly cylindrical end, such that, for example, some embodiments may feature opening similar to that depicted by FIGS. 8G and 8H but with a closed end approximating that of the opening depicted by FIGS. 8E and 8F. Further, as noted above, a plunger might have a different cross-sectional shape, and/or an opening might have a different cross-sectional shape. Based on the disclosure herein, those skilled in the art will recognize that other variations and modifications are possible as well, without varying from the scope of the invention.

Turning now to FIG. 9, a chart 900 illustrates the leakage performance of various facial profiles during the pumping of water, demonstrating some of the performance advantages of various embodiments of the invention. The tests illustrated by the chart 900 were all performed with a piston pump having a plunger three-eighths inch in diameter with a housing length of 1.158 inches. It should be noted that, while specific leakage data may vary according to application, the relative performance enhancements of different facial profiles may be expected to remain fairly consistent, although certain profiles may be relatively more advantageous under certain circumstances. As illustrated, the leakage of all facial profiles may be roughly equivalent at low pressures. At higher pressures, however, it can be seen that a flat facial profile (i.e., a plunger with no opening in its face) may exhibit relatively large leakage (e.g., approximately 450 ml/hour at 6000 psi). In contrast, a plunger with a hemispherical facial profile (such as that illustrated by FIGS. 8C and 8D), exhibits significantly less leakage at the same pumping pressure (e.g., approximately 250 ml/hour at 6000 psi), and a plunger with a cylindrical facial profile exhibits even less leakage. For instance, a plunger with a cylindrical opening one-quarter inch in diameter and one-half inch deep exhibits approximately 220 ml/hour leakage at 6000 psi, and a plunger with a cylindrical opening one-quarter inch in diameter and one inch deep exhibits approximately 200 ml/hour leakage at the same pressure.

It is believed that these varying facial profiles reduce pump leakage (also referred to as “blow by”) by deforming under the pressure of the fluid being pumped, thereby reducing the clearance between the plunger and the plunger housing, and consequently reducing the available area for the fluid to flow between the plunger and the housing. In some embodiments, therefore, the plunger and housing may be configured so that the opening extends into the portion of the plunger that remains within the housing even when the plunger is fully-extended, ensuring that a deformed portion of the plunger remains within the housing at all times during operation.

Although the facial openings described herein can provide enhance leakage performance when used with a wide variety of plungers and/or housings, such openings are particularly advantageous when used with ceramic plungers and/or housings (including without limitation plungers and/or housings comprising any of the materials described in detail above), due to the relative rigidity and durability of ceramics over other materials, such as steel and other metals. Merely by way of example, ceramic plungers can tolerate relatively higher pressures without excessive deformation. In addition, the hardness of ceramics allows such plungers and/or housings to have longer operating lives, as described above, relative to their metal counterparts. Because the facial openings reduce the clearance between the plunger and the housing, this enhanced durability can be advantageous when such openings are employed.

Those skilled in the art will recognize that embodiments of the invention can include any of the face profiles described above, as well as others. The choice of face profile can depend on the fluid pressure exhibited by the material being pumped as well as other qualities of the fluid and/or plunger, e.g., viscosity and/or Reynolds numbers of the fluid, length of the plunger housing, tolerance between plunger and the housing, etc., as such characteristics are described above.

In some cases, a plunger (of whatever facial profile and/or composition) may be coupled with a thrust rod adaptor (and/or any other mechanism for driving and/or axially displacing the plunger) via a coupling assembly, which can, in some embodiments, be a flexible coupling assembly. A flexible coupling assembly can be used to allow a plunger to be driven and/or displaced in a direction different than the direction of the driving mechanism's movement. Further, a flexible coupling assembly may be used to allow for acceptable operation of a pump even when the plunger is not perfectly aligned axially with the driving mechanism, providing a greater tolerance for misalignment than other coupling assemblies.

Merely by way of example, FIG. 10A illustrates a drive element 1000 (which, in the exemplary illustration is a thrust rod but could also be any other suitable component) and a plunger 1020. The thrust rod 1000, which can be fashioned, machined, cast, etc. from any suitable material, including without limitation steel and/or other metals, ceramics, and/or the like, can comprise a thrust rod body 1004 and a means for attaching the thrust rod to a driving apparatus (such as a diaphragm motor, as described above, or any other mechanism which can provide for movement of the thrust rod). Such means can include, for example, a coupling notch 1008 or any other suitable attachment mechanism, such as clips, threaded adaptors, and/or the like. The thrust rod 1000 can also comprise a collar 1012, which can function to prevent a flexible coupling assembly (described in more detail below) from sliding along the length of the thrust rod 1000. The thrust rod 1000 can, in some embodiments, further feature recesses or other devices to allow for more secure attachment of the coupling assembly to the thrust rod 1000. In the illustrated embodiment, for example, the thrust rod 1000 features an annular recess 1016, which can allow for the attachment of an appropriate clip, as described in detail below. Other embodiments may include protrusions, slots (e.g., for the insertion of a cotter pin), flattened surfaces and/or the like, which also can facilitate the attachment of the coupling assembly to the thrust rod 1000. Likewise, the plunger 1020 (which can be, inter alia, any of the plungers described elsewhere herein) may feature similar devices, such as the annular recess 1024, and/or a collar (not shown in FIG. 10A).

Turning now to FIG. 10B, the thrust rod 1000 and plunger 1020 of FIG. 10A are shown coupled with a flexible coupling assembly, which includes a coupling member 1028 that is disposed over opposing ends of the rod 1000 and plunger 1020. Further, one (or more) fastening devices 1032 a and 1032 b can be used to fasten the coupling member 1028 to the rod 1000 and plunger 1020, respectively. Merely by way of example, in accordance with some embodiments, a nine-sixteenths inch hose clamp, such as part no. 4E587 from W.W. Grainger, Inc. of Lake Forest, Ill., may be used as a fastening device. As noted above, other fastening devices may be used as well. Alternatively, the coupling member 1028 may be formed integrally with the thrust rod 1000 and/or the plunger 1020, which may obviate the need for one or more of the fastening devices.

As mentioned above, in accordance with certain embodiments, the coupling member 1028 may be flexible. Merely by way of example, some embodiments feature a length of five-sixteenths inch (inner diameter) reinforced PVC tubing as a coupling member. (The size of the coupling member may depend on the size of the plunger.) Other, similar materials may be used as well, depending on the application and the desired degree of flexibility. For example, steel tubing and/or tubing reinforced with Kevlar®, metallic cladding and/or sheathing, etc. may be used for additional durability. This flexibility allows for the plunger 1020 to be operated in a somewhat unaligned direction, relative to the axial direction of the thrust rod 1000, as depicted by FIG. 10C. This flexibility also provides enhanced compatibility with ceramic plungers and/or housings, which may sometimes be relatively intolerant.

Another set of embodiments provides methods of producing and/or using pumps and/or plungers. Merely by way of example, FIG. 11 illustrates a method 1100 of producing/implementing pumps and plungers, in accordance with some such embodiments. At block 1104, a plunger may be provided. The plunger may be constructed of any material, including, inter alia, the materials discussed above, and may feature any appropriate facial profile, including, inter alia, the facial profiles discussed above. In accordance with some embodiments, providing a plunger can comprise machining and/or otherwise modifying the plunger to describe an appropriate facial profile. Merely by way of example, a plunger with a generally flat facial profile might be machined with a die having an appropriate shape to impart the desired facial profile. Alternatively and/or in addition, a plunger may be cast/molded (and/or otherwise formed) with a desired facial profile.

At block 1108, a drive element may be provided. The drive element can comprise any of the components described above. For example, the drive element can comprise a thrust rod (also described as a “thrusting rod”) or similar component. The plunger may be coupled with the drive element (block 1112) using any suitable method and/or mechanism. In some embodiments, coupling the plunger with the drive element can comprise coupling the plunger and the drive element using a coupling assembly, including without limitation a flexible coupling assembly, some exemplary embodiments of which are described with respect to FIGS. 10A-10C, above. If necessary, the drive element and the plunger may be aligned (block 1116), e.g., to ensure that the drive element properly drives the plunger to pump a fluid when in operation. In some cases, it may be necessary that the plunger and drive element be axially aligned with a relatively high degree of precision, to ensure proper operation. In other cases, however, such as when a flexible coupling assembly is used for example, it may be possible to align the drive element and the plunger with a relative lower degree of precision. In fact, in some cases (again, for example, when using a flexible coupling assembly), the drive element and the plunger need not be axially aligned but instead may have a degree of alignment offset, as discussed above.

The drive element may be connected with a drive mechanism (block 1120). As used in this section, the term drive mechanism should be understood to mean any source that can provide movement of the drive element and/or plunger sufficient to operate the plunger in such a way as to pump a fluid. Merely by way of example, any such movement source discussed above (including without limitation a diaphragm motor, an electric motor, an internal combustion engine, etc.) may be used as a drive mechanism to drive the drive element and/or plunger. Finally, the pump may be operated (block 1124), for instance by operating the drive mechanism to drive the drive element, and/or by extension, the plunger, thereby reciprocally moving the plunger in and out of (or within) a pump chamber, which can allow for the pumping of fluids.

Based on the disclosure herein, one skilled in the art can appreciate that the reciprocal motion of the plunger relative to the pump chamber often will impose a pressure on the fluid within the pump chamber, thereby effecting the pumping of the fluid. Conversely, the fluid may exert a corresponding pressure on the plunger, and in particular on the facial profile of the plunger (block 1128). This pressure can cause the deformation of at least a portion of the plunger (block 1132). The nature of the deformation may depend on the shape of any opening defined by the facial profile of the plunger, as described above, and the deformation may, in some cases, reduce the clearance (tolerance) between the plunger and a housing surrounding the plunger. As described above, plunger pumps often exhibit leakage between the plunger and the housing (i.e., along the length of the plunger), and this reduction in clearance can result in a reduced area through which the fluid may escape between the plunger and the housing, thereby reducing the relative amount of leakage along the length of the plunger (block 1136).

In this way, embodiments of the invention provide plungers, plunger assemblies, and pumps, as well as methods for producing and/or implementing them. The description above identifies certain exemplary embodiments for implementing the invention, but those skilled in the art will recognize that many modifications and variations are possible within the scope of the invention. The invention, therefore, is defined only by the claims set forth below. 

1. A plunger assembly for use in a pump, the plunger assembly comprising: a plunger having an axis, a first end portion and a second end portion, the first end portion being configured to be coupled with a flexible coupling assembly and the second end portion being configured to be exposed to a pump chamber, such that a reciprocal motion of the plunger along the axis of the plunger can result in the pumping of a fluid through the pump chamber; a drive element having an axis, the drive element being configured for reciprocal motion along the axis of the drive element; and a flexible coupling assembly coupled with the first end portion of the plunger and further coupled with the drive element, the flexible coupling assembly being configured to translate the reciprocal motion of the drive element to the plunger, causing a reciprocal motion of the plunger along the axis of the plunger.
 2. A plunger assembly as recited in claim 1, wherein the flexible coupling assembly comprises a length of PVC tubing.
 3. A plunger assembly as recited in claim 1, wherein the drive element is configured to be coupled with a drive mechanism capable of providing the reciprocal motion of the drive element.
 4. A plunger assembly as recited in claim 1, wherein the axis of the plunger and the axis of the drive element are generally axially aligned.
 5. A plunger assembly as recited in claim 4, wherein the flexible coupling assembly is configured to allow the axis of the plunger and the axis of the drive element to be aligned relatively imprecisely.
 6. A plunger assembly as recited in claim 1, wherein axis of the plunger and the axis of the drive element are not axially aligned, and wherein the flexible coupling assembly is configured to translate the reciprocal motion of the drive element to the plunger, causing a reciprocal motion of the plunger along the axis of the plunger, even though the respective axes of the drive element and the plunger are not axially aligned.
 7. A plunger assembly as recited in claim 1, wherein the plunger comprises a metal.
 8. A plunger assembly as recited in claim 1, wherein the plunger comprises a ceramic material.
 9. A plunger assembly as recited in claim 8, wherein the plunger comprises a material selected from the group consisting of aluminum oxide, transformation-toughened zirconia, and approximately 99.5 percent Al₂O₃.
 10. A plunger assembly as recited in claim 1, wherein the plunger is generally cylindrical in shape.
 11. A plunger assembly as recited in claim 10, wherein the plunger is between about one-quarter inch and about three inches in diameter.
 12. A plunger assembly as recited in claim 1, wherein the plunger is configured to be slidably disposed at least partially within a plunger housing, and wherein the second end portion has a facial profile defining an opening and is configured to be exposed to a pump chamber and in contact with a fluid, such that a reciprocal motion of the plunger with respect to the pump chamber exerts a pressure on the fluid, allowing the fluid to be pumped, such that, when the plunger is in contact with the fluid, the fluid exerts sufficient pressure on the facial profile to cause a deformation of at least part of the plunger.
 13. A plunger for use in a pump, the plunger comprising a first portion configured to be slidably disposed at least partially within a plunger housing and a second portion having a facial profile defining an opening, the second portion being configured to be exposed to a pump chamber and in contact with a fluid, such that a reciprocal motion of the plunger with respect to the pump chamber exerts a pressure on the fluid, allowing the fluid to be pumped, wherein, when the plunger is in contact with the fluid, the fluid exerts sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger.
 14. A plunger as recited in claim 13, wherein the plunger has an exterior diameter configured to fit an interior diameter of the plunger housing to within a certain tolerance when no pressure is applied to the facial profile, such that when the fluid exerts sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger, the deformation reduces the certain tolerance.
 15. A plunger as recited in claim 13, wherein the sufficient pressure exerted on the facial profile to cause a deformation of the second portion of the plunger is between about 500 pounds per square inch and about 6000 pounds per square inch.
 16. A plunger as recited in claim 13, wherein the reciprocal motion of the plunger results in a certain amount of leakage of the fluid along the length of the plunger, and wherein the deformation of the second portion of the plunger functions to reduce the certain amount of leakage.
 17. A plunger as recited in claim 13, wherein the plunger comprises a metal.
 18. A plunger as recited in claim 13, wherein the plunger comprises a ceramic material.
 19. A plunger as recited in claim 18, wherein the plunger comprises a material selected from the group consisting of aluminum oxide, transformation-toughened zirconia, and approximately 99.5 percent Al₂O₃.
 20. A plunger as recited in claim 13, wherein the plunger is generally cylindrical in shape.
 21. A plunger as recited in claim 13, wherein the facial profile defines an opening that is generally cylindrical in shape.
 22. A plunger as recited in claim 21, wherein a ratio of a cross-sectional diameter of the opening defined by the facial profile to a cross-sectional diameter of the plunger is between about 0.3 and about 1.0.
 23. A plunger as recited in claim 21, wherein the facial profile defines an opening with a cross-section that is between about one-eighth inch and about three inches in diameter.
 24. A plunger as recited in claim 21, wherein the facial profile defines an opening that is between about three-eighths inch and about one-and-one-quarter inch in length.
 25. A plunger as recited in claim 13, wherein the facial profile defines an opening that is roughly hemispherical in shape.
 26. A plunger as recited in claim 25, wherein the facial profile defines an opening with a diameter approximately equal to a cross-sectional diameter of the plunger.
 27. A plunger as recited in claim 25, wherein ratio of a diameter of the opening defined by the facial profile to a cross-sectional diameter of the plunger is between about 0.3 and about 1.0.
 28. A plunger as recited in claim 13, wherein the facial profile defines an opening with a keyhole shape.
 29. A plunger as recited in claim 13, wherein the facial profile defines a channel in a face of the plunger.
 30. A plunger as recited in claim 29, wherein a length of the channel spans a cross-sectional diameter of the plunger.
 31. A plunger as recited in claim 29, wherein a width of the channel is about one-quarter to about three-quarters of a cross-sectional diameter of the plunger.
 32. A plunger as recited in claim 13, wherein the plunger is configured to be coupled with a flexible coupling assembly.
 33. A method of using a plunger to pump fluids, the method comprising: providing a plunger having an axis, a first portion and a second portion, the first portion being configured to be coupled with a drive element and the second portion being configured to be exposed to a pump chamber, such that a reciprocal motion of the plunger along the axis of the plunger can result in the pumping of a fluid through the pump chamber; providing a drive element having an axis, the drive element being configured for reciprocal motion along the axis of the drive element; coupling the drive element with the first portion of the plunger using a flexible coupling assembly, the flexible coupling assembly being configured to translate the reciprocal motion of the drive element to the plunger, causing a reciprocal motion of the plunger along the axis of the plunger; and imparting a reciprocal motion to axis of the drive element, thereby causing the plunger to move in a reciprocal motion along the axis of the plunger.
 34. A method of using a plunger to pump fluids as recited in claim 33, wherein the plunger is configured to be slidably disposed at least partially within a plunger housing, and wherein the second portion has a facial profile defining an opening and is configured to be exposed to a pump chamber and in contact with a fluid, the method further comprising: exerting sufficient pressure on the facial profile of the plunger to cause a deformation of at least part of the plunger.
 35. A method of using a plunger to pump fluids as recited in claim 34, wherein the plunger has an exterior diameter configured to fit an interior diameter of the plunger housing to within a certain tolerance when no pressure is applied to the facial profile, such that when sufficient pressure is exerted on the facial profile to cause a deformation of at least part of the plunger, the deformation reduces the certain tolerance.
 36. A method of using a plunger to pump fluids as recited in claim 35, wherein the reciprocal motion of the plunger results in a certain amount of leakage of the fluid along the length of the plunger, and wherein the deformation of the second portion of the plunger functions to reduce the certain amount of leakage.
 37. A method of using a plunger to pump fluids as recited in claim 33, wherein the plunger comprises a metal.
 38. A method of using a plunger to pump fluids as recited in claim 33, wherein the plunger comprises a ceramic material.
 39. A method of using a plunger to pump fluids, the method comprising: providing a plunger comprising a first portion configured to be slidably disposed at least partially within a plunger housing and a second portion having a facial profile defining an opening, the second portion being configured to be exposed to a pump chamber and in contact with a fluid, such that a reciprocal motion of the plunger with respect to the pump chamber can exert pressure on the fluid, allowing the fluid to be pumped, wherein, when the plunger is in contact with the fluid, the fluid exerts sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger; and moving the plunger in a reciprocal motion along the axis of the plunger.
 40. A method of using a plunger to pump fluids, as recited in claim 39, wherein the plunger has an exterior diameter configured to fit an interior diameter of the plunger housing to within a certain tolerance when no pressure is applied to the facial profile, such that when the fluid exerts sufficient pressure on the facial profile to cause a deformation of the second portion of the plunger, the deformation reduces the certain tolerance.
 41. A method of using a plunger to pump fluids, as recited in claim 39, wherein the sufficient pressure exerted on the facial profile to cause a deformation of the second portion of the plunger is between about 500 pounds per square inch and about 6000 pounds per square inch.
 42. A method of using a plunger to pump fluids, as recited in claim 39, wherein the reciprocal motion of the plunger results in a certain amount of leakage of the fluid along the length of the plunger, and wherein the deformation of the second portion of the plunger functions to reduce the certain amount of leakage.
 43. A method of using a plunger to pump fluids, as recited in claim 39, wherein the plunger comprises a metal.
 44. A method of using a plunger to pump fluids, as recited in claim 39, wherein the plunger comprises a ceramic material.
 45. A plunger pump assembly, comprising: a pump body defining a pump chamber with an inlet port and an outlet port, wherein the pump body further defines a plunger port disposed between the inlet port and the outlet port; a first check valve in fluid communication with the inlet port of the pump chamber, wherein the first check valve is configured to allow a fluid to flow only into the pump chamber; a second check valve in fluid communication with the outlet port of the pump chamber, wherein the second check valve is configured to allow the fluid to flow only out of the pump chamber; a plunger housing defining a cylindrical bore having an interior diameter, wherein the plunger housing is disposed within the plunger port; and a plunger having an exterior diameter and comprising a portion with a facial profile defining an opening, wherein the plunger is slidably disposed within the cylindrical bore such that when the plunger is reciprocated back and forth within the bore, the fluid is moved from the inlet port of the pump chamber to the outlet port of the pump chamber, and wherein when the facial profile of the plunger is in contact with the fluid, the fluid exerts sufficient pressure on the facial profile to cause a deformation of at least part of the plunger.
 46. The plunger pump assembly of claim 45, wherein the plunger is coupled with a flexible coupling assembly, the flexible coupling assembly being further coupled with a drive system, such that the drive system may impart, via the flexible coupling assembly, reciprocating force on the plunger sufficient to reciprocate the plunger back and forth within the bore.
 47. The plunger pump assembly of claim 46, wherein the flexible coupling assembly comprises PVC tubing.
 48. The plunger pump assembly of claim 45, wherein the exterior diameter of the ceramic plunger fits the interior diameter of the bore to within a certain tolerance when no pressure is exerted on the facial profile of the plunger.
 49. The plunger pump assembly of claim 48, wherein the deformation of at least part of the plunger is sufficient to reduce the certain tolerance.
 50. The plunger pump assembly of claim 48, wherein the certain tolerance is in the range from about 1.0 microns to about 6.0 microns.
 51. The plunger pump assembly of claim 45, wherein at least one of the plunger and the plunger housing comprises a ceramic material.
 52. The plunger pump assembly of claim 51, wherein at least one of the plunger and the plunger housing comprises a material selected from the group consisting of aluminum oxide, transformation-toughened zirconia, and approximately 99.5 percent Al₂O₃.
 53. The plunger pump assembly of claim 45, wherein a surface of the plunger defines at least one discontinuity, and wherein the discontinuity is configured to reduce the escape of the fluid through the bore.
 54. A fluid injection system, comprising: a drive system configured to impart a generally reciprocal force on a plunger; and a plunger pump assembly, wherein the plunger pump assembly comprises: a pump body defining a pump chamber with an inlet port and an outlet port, wherein the pump body further defines a plunger port disposed between the inlet port and the outlet port; a first check valve in fluid communication with the inlet port of the pump chamber, wherein the first check valve is configured to allow a fluid to flow only into the pump chamber; a second check valve in fluid communication with the outlet port of the pump chamber, wherein the second check valve is configured to allow the fluid to flow only out of the pump chamber; a plunger housing defining a cylindrical bore having an interior diameter, wherein the plunger housing is disposed within the plunger port; and a plunger having an exterior diameter and comprising a portion with a facial profile defining an opening, wherein the plunger is slidably disposed within the cylindrical bore and coupled with the drive system, such that when the plunger is reciprocated back and forth within the bore, the fluid is moved from the inlet port of the pump chamber to the outlet port of the pump chamber, and wherein when the facial profile of the plunger is in contact with the fluid, the fluid exerts sufficient pressure on the facial profile to cause a deformation of at least part of the plunger.
 55. The fluid injection system of claim 54, wherein the plunger is coupled with a flexible coupling assembly, the flexible coupling assembly being further coupled with the drive system, such that the drive system may impart, via the flexible coupling assembly, reciprocating force on the plunger sufficient to reciprocate the plunger back and forth within the bore.
 56. The fluid injection system of claim 55, wherein the flexible coupling assembly comprises PVC tubing.
 57. The fluid injection system of claim 54, wherein the drive system comprises a diaphragm motor dynamically coupled with the plunger and configured to reciprocally slide the plunger back and forth in the bore, thereby moving fluid from the inlet port of the pump chamber to the outlet port of the pump chamber.
 58. The fluid injection system of claim 54, further comprising a fluid source in fluid communication with the first check valve and operable to supply a fluid to the inlet port.
 59. The fluid injection system of claim 57, wherein the diaphragm motor comprises a diaphragm and a linkage, wherein the linkage is coupled with the diaphragm and further with the plunger, wherein the fluid source is a first fluid source, the system further comprising a second fluid source in fluid communication with the diaphragm motor and operable to supply a pressurized second fluid to the diaphragm motor, and wherein the diaphragm motor is configured to reciprocally slide the plunger back and forth in the bore in response to a fluid pressure imposed on the diaphragm by the second fluid.
 60. The fluid injection system of claim 54, wherein at least one of the plunger and the plunger housing comprises a ceramic material. 